Answer:
C. Arabic language
Step-by-step explanation:
The Abbasid caliphate (750-1258), also called abbasid caliphate, was a Caliph dynasty founded in 750 by Abu l-Abbas, descendant of Abbas, uncle of Muhammad, who took power after eliminating the Umayyad dynasty and moved the capital of Damascus Baghdad. Baghdad became one of the main centers of world civilization during the caliphate of Harun al-Rashid, character of the Arabian Nights.
During this caliphate, the economy of the empire was improved, achieved great prosperity, introduced Arabic as the official language and letters and sciences flourished under this dynasty. The Abbasid Caliphate was the founder of Baghdad.